What are the recommended HIV testing guidelines, including who should be screened, which tests to use, and how to interpret and follow up on the results?

HIV Testing Guidelines

All adolescents and adults aged 15 to 65 years should be screened for HIV at least once, with high-risk populations requiring annual or more frequent screening. 1

Who Should Be Screened

Universal Screening Population

• All persons aged 15-65 years should undergo routine HIV screening regardless of risk factors 1
• All pregnant women during each pregnancy, including those who present in labor with unknown HIV status 2, 1
• Younger adolescents (<15 years) and older adults (>65 years) should be screened if they have any increased risk factors 1

High-Risk Populations Requiring More Frequent Screening

Annual screening is recommended for: 2, 3

• Men who have sex with men (MSM)
• Persons with multiple sexual partners or unprotected sex
• Current or past injection drug users
• Persons who exchange sex for money or drugs
• Individuals whose sexual partners are HIV-positive, bisexual, or injection drug users
• Persons being treated for sexually transmitted diseases
• Persons with blood transfusions between 1978-1985

Consider screening every 3-6 months for: 3

• MSM at particularly high risk based on individual risk factors and local HIV epidemiology, though evidence remains insufficient to mandate this frequency over annual screening

High-Risk Clinical Settings

Priority screening locations include STD clinics, correctional facilities, homeless shelters, tuberculosis clinics, substance abuse clinics, and adolescent health clinics with high STD prevalence 2

Which Tests to Use

Current Testing Algorithm (Fourth-Generation Approach)

Initial screening: 4

• Use a combination immunoassay that detects both HIV-1/HIV-2 antibodies AND HIV-1 p24 antigen
• This reduces the window period to 11-14 days post-infection 5

For reactive initial tests: 4

• Perform an HIV-1/HIV-2 antibody differentiation immunoassay
• This distinguishes between HIV-1 and HIV-2 infections

For discordant results: 4

• If initial test is reactive but differentiation assay is nonreactive or indeterminate, proceed to HIV-1 nucleic acid testing (NAT) for resolution

Special Testing Considerations

Acute HIV infection: 2

• Patients presenting with viral syndrome suggestive of acute HIV may require nucleic acid testing in addition to antibody tests, as antibody tests may be negative during the acute window period

Rapid vs. traditional testing: 2

• Traditional enzyme immunoassay followed by Western blot has very high sensitivity and specificity with rare false-positives
• Rapid tests provide results within 1 hour, significantly increasing the proportion of patients who receive their results

Prevalence Thresholds

Routine screening is recommended unless HIV prevalence is <0.1% 2

Practical implementation approach: 2

• Begin routine screening in your population
• If no HIV-infected patients are identified after screening approximately 4,000 patients, the 95% confidence interval for prevalence will be <0.1%, and you should reassess the need for continued routine screening

Follow-Up and Counseling

Patient Education

• Discuss HIV risk factors with all patients, particularly adolescents and older adults who may be unaware of risky behaviors 2
• Patients should be notified that testing will be performed but can decline (opt-out approach) 6

Key Implementation Points

• The shift from risk-based to routine screening occurred because risk-based approaches failed to identify a substantial proportion of HIV-infected individuals 2
• Early identification and treatment substantially reduces AIDS-related events, death, and transmission to uninfected partners 1
• Treatment of pregnant women dramatically reduces mother-to-child transmission 1

Common Pitfalls to Avoid

• Don't rely solely on risk assessment - many HIV-infected individuals are missed by risk-based screening alone 2
• Don't forget older adults - approximately 20% of HIV patients are over age 50, and screening up to age 75 can be cost-effective in sexually active populations with prevalence >0.1% 2
• Don't use outdated testing algorithms - the combination antigen/antibody test with differentiation assay has replaced the traditional Western blot confirmation approach 4
• Don't assume one negative test is sufficient for high-risk patients - annual or more frequent rescreening is essential for ongoing risk 3